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Guidelines for Endothelial Testing

Does breaking up prolonged sitting improve cognitive functions in sedentary adults?

Med Sci Sports Exerc 2021 Jul 29.
The Acute Effects of Prolonged Uninterrupted Sitting on Vascular Function: A Systematic Review and Meta-analysis
Objective: To determine the dose-response relationship between prolonged sitting and vascular function in healthy individuals and those with metabolic disturbances. To investigate the acute effects, on vascular function, of interventions that target interrupting prolonged sitting.
Design: Systematic review with meta-analysis.
Data sources: Ovid Embase, Ovid Medline, PubMed, and CINAHL were searched from inception to 4 December 2020.
Eligibility criteria: Randomised crossover trials, quasi-randomised trials, and parallel group trials where vascular function (flow-mediated dilation, FMD) was assessed before and after an acute period of sedentary behaviour.
Results: Prolonged sitting resulted in a significant decrease in the standardised mean change (SMC) for lower-limb FMD at the 120-min (SMC = -0.85, 95%CI -1.32 to -0.38) and 180-min (SMC = -1.18, 95%CI -1.69 to -0.66) time points. A similar pattern was observed for lower-limb shear rate. No significant changes were observed for any outcomes in the upper limb. Subgroup analysis indicated that prolonged sitting decreased lower-limb FMD in healthy adults (SMC = -1.33, 95%CI -1.89 to -0.78) who had higher a priori vascular endothelial function, but not in those with metabolic and vascular dysfunction (SMC = -0.51, 95%CI -1.18 to 0.15). Interrupting sitting with active interruptions increased the standardised mean difference for FMD, relative to prolonged sitting, but it was not statistically significant(0.13, 95%CI -0.20 to 0.45).
Conclusion: Lower-limb vascular function is progressively impaired as a consequence of prolonged sitting, up to 180 min. A similar trend was not observed in upper-limb vascular function. Subgroup analysis indicated prolonged sitting negatively impacts healthy populations, a finding not observed in those with metabolic disturbances. Regularly interrupting sitting with activity may be beneficial for those with metabolic disturbances.
Copyright © 2021 American College of Sports Medicine.
BMC Musculoskelet Disord
2021 Mar 12;22(1):274
Does breaking up prolonged sitting improve cognitive functions in sedentary adults? A mapping review and hypothesis formulation on the potential physiological mechanisms
Background: Prolonged (excessive) sitting is detrimentally associated with cardiovascular, metabolic and mental health. Moreover, prolonged sitting has been associated with poor executive function, memory, attention and visuospatial skills, which are important cognitive aspects of work performance. Breaking up prolonged sitting with standing or light-intensity exercises at the workplace is recognized as a potential measure in improving cognition. However, preliminary evidence, primarily from acute laboratory experiments, has enabled formulating hypothesis on the possible mechanistic pathways. Hence, the aim of this mapping review is to gather preliminary evidence and substantiate possible physiological mechanisms underpinning the putative effects of breaking prolonged sitting on improving cognitive function among sedentary office workers.
Mapping method: We searched four databases to identify relevant studies that explored the effects of uninterrupted sitting on cognitive function. First, we introduce how prolonged sitting increases the risks of hyperglycemia, autonomic stability, inflammation, adverse hormonal changes and restrictions in cerebral blood flow (CBF) and alters cognitive function. Second, we elucidate the direct and indirect effects of breaking up prolonged sitting time that may prevent a decline in cognitive performance by influencing glycaemic variability, autonomic stability, hormones (brain derived neurotrophic factor, dopamine, serotonin), vascular functions, and CBF. We highlight the importance of breaking up prolonged sitting on metabolic, vascular and endocrine functions, which in turn may improve cognitive functions and eventually foster work productivity. Improved synaptic transmission or neuroplasticity due to increased brain glucose and mitochondrial metabolism, increased endothelial shear and CBF, increased brain neurotrophic factors (dopamine) and accelerated anti-inflammatory functions are some of the hypothetical mechanisms underpinning improved cognitive functions.
Conclusion: We postulate that improving cognitive function by breaking up prolonged sitting periods is biologically plausible with the myriad of (suggested) physiological mechanisms. Future experimental studies to ascertain the aforementioned hypothetical mechanisms and clinical trials to break sedentary behavior and improve cognitive functions in sedentary office workers are warranted.
Keywords: Brain health; Cognitive function; Executive functions; Physiology; Sitting; Workplace.
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